Radio Frequency Interference Suppression Algorithm in Spatial Domain for Compact High-Frequency Radar

An Orthogonal Projection Algorithm to Suppress Interference in High-Frequency Surface Wave Radar

“…This scheme was first proposed in [21] based on two crossed-loop/monopole antennas in which the far-range bins of two antenna channels were used to estimate the covariance matrix. The scheme was improved in [22], which used range bins between 60 and 120 as far-range bins. Its performance was severely limited by the insufficient degree of freedom.…”

“…In recent years, a new tool for interference mitigation known as the orthogonal projection algorithm has been rapidly developed [19][20][21][22][23]. The key to orthogonal projection is to select secondary data for obtaining the interference subspace, and the mixture signals that include sea echoes and interference then can be orthogonally projected onto the interference subspace to suppress interference.…”

“…For now, orthogonal projection methods have been implemented in both the time domain and the Doppler domain for RFI cancellation. In the time domain, the interference covariance matrix can be estimated by using information about either the range and sweep (represents time series) dimensions [19,20] or the range and antenna channel dimensions [21,22], and in the Doppler domain, the orthogonal projection method has been performed using range and frequency dimensions [23]. However, these methods have not yet been used for ionospheric cancellation and may be associated with the following two problems: (1) The radar detection range is limited to the bandwidth of the low-pass filter, which, to avoid range aliasing, cannot exceed half of the transmit-receive (T/R) pulse frequency.…”

Fractional Fourier Transform-Based Radio Frequency Interference Suppression for High-Frequency Surface Wave Radar

“…However, target signal can easily be included in the interference training and be cancelled subsequently. The orthogonal projection methods have been developed for RFI suppression [13][14][15][16][17]. The processing is mainly implemented in either the time domain or the Doppler domain.…”

“…The processing is mainly implemented in either the time domain or the Doppler domain. In time domain, the interference covariance matrix can be estimated by using information about the range and sweep dimensions [13,14], the range and antenna channel dimensions [15], or the antenna channels and sweep dimensions [16]. In Doppler domain, the orthogonal projection methods has been performed using information about the range and frequency dimensions [17].…”